Online is best now with unacademy,as it costs less and there is quality,if you want to compare online vs offline,then watch this video 

Preference for Online vs. Offline Exams in JEE Mains
The choice between online and offline exams for JEE Mains has been a topic of discussion among students and educators. Each format has its own set of advantages and disadvantages.
Advantages of Online Exams
- Immediate Results: Online exams often provide instant results, allowing students to quickly assess their performance.
- Flexible Scheduling: They can be scheduled at various times, accommodating students' preferences and reducing stress.
- Less Paper Waste: An online format is more environmentally friendly, as it eliminates the need for printed question papers.
Advantages of Offline Exams
- Familiarity: Many students are more accustomed to taking exams on paper, which can reduce anxiety.
- Easier Navigation: Some students find it easier to navigate through questions and make annotations on paper.
- Less Technical Issues: Offline exams eliminate concerns related to internet connectivity and technical glitches that can occur during online tests.
Student Opinions
- Preference for Online: Many tech-savvy students prefer online exams for their convenience and the modern approach they offer.
- Preference for Offline: Others feel more comfortable with traditional paper-based tests, valuing the tactile experience and reduced reliance on technology.
Conclusion
Ultimately, the preference between online and offline exams for JEE Mains varies among students, depending on their comfort level with technology and testing environments. It is essential for students to choose the format that best suits their study habits and test-taking strategies.